1. Field of the Invention
The present invention relates to a system of identification between at least one interrogation station or interrogator and at least one, and possibly a plurality of, response stations or responder units.
And more particularly, the invention is applicable to the identification of a responder unit from an interrogation station; one of the two elements, either the responder unit or the interrogator, is mobile with respect to the other and identification is obtained without contact; transfer of the data being effected by radio waves.
2. Background Art
Numerous systems of this type which allow identification of a responder unit are known, and FIG. 1 illustrates the various functions performed within the framework of the presently known interrogation systems which are followed by an identification response.
According to FIG. 1, it is seen that an interrogation station 1 (fixed or mobile) emits a coded signal 5 on a radio wave length in particular and preferably on a submetric wave length.
More especially, UHF radio waves are used; the term "UHF wave" is used in the course of the present specification to designate radio frequency waves higher than 100 MHz.
To that end, the interrogation station or interrogator 1 comprises a wave generator or oscillator 4 which supplies the antenna 3 for the emission of the interrogation wave 5. This signal is picked up by the antenna 6 of a badge 2 which may transmit the signal to the detector 7 which alerts the control electronics 8, which triggers off, on the one hand, the memorizing of the signal picked up in the floating memory 9 as well as the supply of the modulator 10.
The signal is received by the badge 2 after modulation has taken place and is transmitted to antenna 3 which re-emits (echos) a response wave 11 of the same kind as the interrogation wave, but after modulation has taken place.
This wave is received in turn by antenna 3 of the fixed station and is processed by the mixer 12 with a view to extracting a low-frequency signal which corresponds to the modulation of the carrier wave; this low-frequency signal after amplification in 14 is processed in a microprocessor 13 in order, in particular, to analyze the signal and to determine the contents of the data.
This same device, limited to the interrogator, is illustrated by the diagram of FIG. 2.